The present invention relates to a clamping device for a telescopic tube.
The present invention also relates to a telescopic pole equipped with a clamping device.
Telescopic tubes nesting in one another are used for varying the length of the object they constitute. It is possible to envisage round tubes or tubes having sections of different shapes, such as oval or square sections. The use of such tubes is extensive and is envisaged for, for example, telescopic ski poles, telescopic hiking poles, tubes for bicycles (saddle, handlebars), for scooters, etc.
Telescopic poles are made up of a number of tubes with sections of different sizes, which are tightly nested and then joined together firmly. Two main clamping systems are used for effecting the locking of a round tube of greater diameter on the round tube of smaller diameter nested directly in it.
Two clamping systems which make it possible to compress the tube of greater diameter on the tube of smaller diameter are known: by rotating a ring, and by tilting an arm. Several systems for clamping by tilting an arm have previously been proposed, either in the form of a collar for securing and coupling pipes or uprights, or intended for telescopic poles.
U.S. Pat. Nos. 4,381,585 and 3,828,403 describe a locking device comprising a split or articulated ring. At one of the open ends of the ring, a first arm is fixed for rotation, and, at its end, an actuating arm is likewise fixed. One of the ends of the actuating arm comprises a cam which interacts with a cam surface located at the other of the open ends of the ring, when the second arm is folded down against the ring.
U.S. Pat. No. 3,305,234 also describes a clamping device comprising a longitudinally open ring. At one of the open ends, a protuberance extends essentially tangentially in relation to the ring. At the end of this protuberance, a curved arm is attached for rotation, and it has a cam interacting with a cam surface located towards the outside of the other open end of the ring.
U.S. Pat. No. 3,084,964 also describes a clamping device of the ball-joint type, comprising a longitudinally split ring passed through by a rod arranged tangentially in the region of the slit. An arm pivots at one of the ends of the rod, and it comprises, towards its pivoting axis, a cam which interacts with a plane surface positioned close to the slit.
EP 0 641 578 and U.S. Pat. No. 5,441,307 describe a clamping device of the ball-joint type intended for a telescopic pole. The clamping device comprises a longitudinally split ring. A tangentially arranged rod passes through the two walls of the slit. A curved arm is fixed to the rod and pivots between a position in which the ring is clamped and a position in which the ring is unclamped.
DE 26 32 201 describes a pole, the handle of which can be locked by virtue of a clamping device of the type with a pivoting monobloc lever having a cam in the region of its pivoting axis. The cam presses towards the top of the handle so as to compress it against the main tube of the pole.
U.S. Pat. No. 2,304,343 describes a device for clamping two telescopic tubes belonging to a lectern, comprising a longitudinally split clamping ring, two wings of which can be clamped by the pivoting of a monobloc arm. At one of its ends, the arm has two protuberances with internal means forming a cam interacting with the two wings of the ring.
EP 0 677 663 describes a clamping device with a longitudinal slit intended for retaining a tube. A pivoting arm comprises, at one of its ends, a spindle and also two lock washers bearing the means forming a cam. The spindle of the arm catches in the device, the two washers with the means forming a cam enclosing the device with the slit. Provided at the other end of the arm are two lugs which interact with two hollows which are formed on a wing arranged on both sides of the slit of the element.
A first disadvantage of these prior clamping devices is that they require a supplementary piece in the form of a shackle or of a second articulated arm. A second disadvantage is that their clamping principle is ineffective on account of the cam acting on only one of the sides of the spacing of the ring. Their assembly is complex and requires a supplementary axis of rotation perpendicular to the first axis passing through in the region of the slit. Play appears in the ball joint as the clamping device is used. Still another disadvantage is the fact that the clamping force occasionally proves to be inadequate for intensive use and for longitudinal stresses applied directly and simultaneously to both tubes.
An object of the present invention is to produce a device for clamping two telescopic tubes with simplified assembly and without the disadvantages of the clamping devices of the prior art. A second object of the present invention is to produce a telescopic pole equipped with such a clamping device.
A first problem consists in producing an effective clamping device which makes it possible to bring the two portions of the longitudinally split ring towards one another simultaneously.
A second problem is to increase the retaining and clamping forces and therefore to enlarge the contact surfaces between moving parts.
A clamping device for two telescopic tubes comprises a ring which is longitudinally split and thus defines a longitudinal spacing located in a plane intersecting the ring longitudinally, said ring being extended towards the outside by two wings facing each other on either side of the longitudinal spacing, at least one rod forming an axis arranged transversely in relation to the plane and passing through the two wings, and an arm which is fixed and pivots in relation to the rod forming an axis, so as to make possible clamping of the ring by reduction of the longitudinal spacing, the two wings being brought towards one another.
According to a first aspect of the present invention, the arm is divided into two branches each having a free end through which the rod forming an axis passes, the two branches and also the free ends coming to lie on either side of the two wings of the ring in order to enclose said two wings.
At least one of the two wings preferably has means forming a cam which interact with means forming a cam located on at least one branch of the arm. The two wings can each have an opening. The rod forming an axis can then pass through the opening of each of these two wings. In a particularly advantageous embodiment, the means forming a cam comprise at least one inclined surface arranged around the openings formed in the two wings. For this reason, these surfaces interact with at least one inclined surface located on at least one free end of the branches of the arm and around the pivoting axis.
In order to avoid any inadvertent unclamping when the ring is clamped, locking means, for example of the catch type, can be provided for securing the arm. These locking means preferably comprise a protuberance positioned on the edge of the ring in the region of the two wings, which interacts with a projection located on the arm. The projection can be positioned in the region of the internal surface of a portion connecting the two branches of the arm.
In an advantageous manner, the locking means are moreover formed by at least one lug which is located on at least one of the two branches of the arm and interacts with at least one hollow located on at least one of the two wings of the ring.
Advantageously, the arm moreover comprises at least one tab extending essentially perpendicularly to at least one of the two branches and in the region of at least one end opposite the two free ends.
According to a second aspect of the present invention, a telescopic pole for skiing or hiking comprises at least two coaxial cylindrical tubes nested one in another and is characterized by at least one clamping device, as described above, slipped around the tube or tubes having the greater diameter.
The tabs located at the end of the arm can come to lie and catch on both sides of a tube having the smaller diameter.